Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/04—Reversed telephoto objectives
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
  • G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
  • G02B13/005—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having spherical lenses only
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/06—Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
  • G02B9/64—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having more than six components

Definitions

• the present invention relates generally to wide angle lenses, and more particularly, but not exclusively, to lenses configured to preferentially image objects located towards the periphery of the field of view, as well as camera systems incorporating such lenses.
• Axiomatic to optical imaging systems is the principle that such systems are designed with the expectation that objects of primary interest will be located on the optical axis of the imaging system, and therefore lenses of such systems must be designed to provide high quality imaging on- axis. Indeed, one will typically accept reduced optical performance at the edges of the field of view in favor of enhanced performance on-axis.
• Photography, microscopy, and astronomy are all examples of fields in which the observer often endeavors to position the optical system so that at least one object of interest is disposed centrally in the field of view on the optical axis.
• the present invention may provide a wide angle lens for imaging objects disposed in a peripheral region of interest of the field of view.
• An exemplary wide angle lens in accordance with the present invention may include, in order along an optical axis from object to image space, a first group of lens elements, an aperture stop, and a second group of lens elements.
• the region of interest may be an annular cone that extends between a first angle of at least 30 degrees from the optical axis to a second angle of at least 75 degrees from the optical axis, where the first and second lens groups are configured for imaging of objects disposed within the region of interest.
• the first angle may be 50 degrees and the second angle may be 100 degrees.
• the lens may be configured and constructed such that a ray of the second angle in object space intersects the lens image plane at a distance, H, from the optical axis and a ray of the first angle in object space intersects the lens image plane at a distance, h, from the optical axis such that H/h > R, or preferably H/h > 1.1 xR, or more preferably H/h > 1.5xR
• the angular mapping of the field of view in the region of interest onto the image plane may be substantially linear.
• the first and second groups of lens elements may be configured for imaging of objects disposed within the region of interest by having certain performance metrics in the region of interest.
• the first and second groups of lens elements may cooperate to provide: a longitudinal spherical aberration on-axis greater than the longitudinal spherical aberration throughout the region of interest; a longitudinal spherical aberration throughout the region of interest less than half of the longitudinal spherical aberration on-axis; a field curvature for tangential rays on-axis greater than the field curvature for tangential rays throughout the region of interest; and/or a field curvature for tangential rays throughout the region of interest less than one quarter of the field curvature for tangential rays on-axis.
• the first and second groups of lens elements may cooperate to provide: a modulation transfer function of at least 55% at 187 lp/mm for sagittal rays in the region of interest; a modulation transfer function of at least 76% at 93 lp/mm for sagittal rays in the region of interest; a modulation transfer function of at least 36% at 187 lp/mm for tangential rays in the region of interest; and/or a modulation transfer function of at least 65% at 93 lp/mm for tangential rays in the region of interest.
• exemplary wide angle lenses in accordance with the present invention may be optimized without the use of aspherical surfaces; the lens elements of the first and second groups may all have spherical surfaces.
• the first group of lens elements may consist of four or five lenses, while the second group of lens elements may consist of four lenses.
• the effective focal length may be 1 mm or less with an f-number of 2.4 or less.
• the present invention may provide a wide angle lens having an angular field of view, FOV, of more than 150 degrees spanning the optical axis and a central half- field of view, FOVi/2, spanning the optical axis.
• the lens may comprise a region of interest disposed between the FOV1/2 and FOV, wherein angular mapping of the field of view in the region of interest onto the image plane is substantially linear.
• the present invention may provide a camera system comprising wide angle lens of the present invention.
• Figure 1 schematically illustrates an exemplary eight element lens in accordance with the present invention
• Figures 2 A - 2C illustrate the calculated longitudinal spherical aberration, field curvature, and f-theta distortion, respectively, of the lens of Fig. 1 ;
• FIG. 3 schematically illustrates an exemplary nine element lens in accordance with the present invention
• Figures 4 A - 4C illustrate the calculated longitudinal spherical aberration, field curvature, and f-theta distortion, respectively of the lens of Fig. 3;
• Figure 5 illustrates the calculated modulation transfer function versus field for the lens of Fig. 3;
• Figure 6 illustrates the calculated polychromatic diffraction modulation transfer function versus spatial frequency for the lens of Fig. 3;
• Figure 7 illustrates calculated spot diagrams for the lens of Fig. 3;
• Figure 8 illustrates the calculated polychromatic diffraction through focus modulation transfer function versus focus shift for the lens of Fig. 3;
• Figure 9 illustrates the calculated relative illumination of the image plane versus field for the lens of Fig. 3;
• Figure 10 illustrates the calculated lens chief ray angle versus field for the lens of Fig. 3 along with the target chief ray angles for an exemplary image sensor (detector).
• Figure 11 illustrates field height versus field of view for the lens of Fig. 3 as designed and fabricated.
• Figures 1 and 3 schematically illustrate configurations of exemplary wide angle lenses 100, 200 optimized for performance towards the outer half of the field-of-view in accordance with the present invention.
• the lenses 100, 200 may have a wide field-of-view of 210° ( ⁇ 105° on either side of the optical axis), and may be optimized for optical performance within a region of interest of the field-of-view.
• the region of interest may comprise an annular cone beginning at 50° from the optical axis and extending to 100° from the optical axis.
• Optical performance outside of the region of interest may be relaxed and have inferior optical performance to that found in the region of interest.
• the spherical aberration of the lenses 100, 200 may be well corrected for 50° and above as compared to 50° and below.
• Applicant has been able to achieve designs in which all optical surfaces are spherical, avoiding the manufacturing complexities and cost associated with aspherical surfaces.
• the lens 100 may include a first group of four optical elements LI - L4 disposed on the object side of an aperture stop SI 1 and may include a second group of four optical elements L6 - L9 disposed on the image side of the stop SI 1, with first-order design properties shown in Table 1.
• the first two lenses, LI, L2 are meniscus-type lenses having surfaces which are convex to the object side, and introduce negative power to decrease entering ray angles to be more parallel to the optical axis.
• the optical glasses provided in Tables 1, 2 refer to glasses from Schott North America, Inc, Elmsford, NY, USA, and Nd refers to a wavelength of 587.6 nm.
• the cyclic olefin copolymer "COC" in Tables 1, 2 may be APELTM Cyclo olefin copolymer APL5014CL (Mitsui Chemicals, Inc., Tokyo, Japan).
• the longitudinal spherical aberration may be well corrected in the region of interest between 50° and 100°, while a relatively large spherical aberration on-axis of 40 ⁇ may be tolerated.
• the longitudinal spherical aberration may be so well corrected in the region of interest that the value in the region of interest may be less than one quarter of that present on-axis.
• field curvature especially for tangential rays, may be minimized in the region of interest while being comparatively larger on-axis, Figs. 2B, 4B.
• the field curvature for tangential rays in the region of interest may be less than one quarter of that present on-axis.
• third order field curvature may be corrected by introducing compensating higher order field curvature via lens element L5 of lens 200, and via lens elements L7, L8.
• F-theta distortion unlike longitudinal spherical aberration and field curvature, may increase with field height without correction, but may be constrained to be less than 34% at full field, Figs. 2C, 4C.
• exemplary target values for the MTF in the region of interest are provided in Table 3, which may be selected with regard to the detector to be used at the image plane.
• the size and spacing of the pixels on the detector can establish the Nyquist frequency for the MTF design targets.
• the Nyquist frequency For example, in the case of an exemplary detector having a pixel size of 1.34 ⁇ x 1.34 ⁇ (OV16825 16-megapixel CameraChipTM sensor, OmniVision Technologies, Inc., Santa Clara, California, USA), one quarter of the Nyquist frequency would correspond to 93 lp/mm, and one half of the Nyquist frequency would correspond to 187 lp/mm.
• the calculated performance for the design of the lens 200 of Fig. 3 with regard to MTF is illustrated in Figs. 5, 6, and 8, as well as Table 4.
• the ability to properly illuminate the detector at the image plane is illustrated in terms of relative illumination in Fig. 9, which illustrates that 80% relative illumination is maintained out to 105°. This result is consistent with proper control of the chief ray angles as illustrated in Fig. 10, which shows that the lens chief ray angle may be maintained ⁇ 2° from the target detector chief ray angle over 60% of field.
• designs in accordance with the present invention may seek to optimize mapping of the angular field-of-view onto the detector in a manner that is both linear in the region of interest (e.g., annular cone beginning at 50° from the optical axis and extending to 100° from the optical axis) and maximizes the number of pixels on the image sensor S20 onto which the region of interest of the field-of-view is mapped.
• region of interest e.g., annular cone beginning at 50° from the optical axis and extending to 100° from the optical axis
• the number of pixels covered on the image sensor may also be optimized in this region, with roughly 970 pixels disposed within the field-of-view between 50° and 100° for the exemplary sensor model OV16825 mentioned above, where the number of pixels is counted along a line taken along one of the two orthogonal directions on which the 1.34 ⁇ x 1.34 ⁇ grid of pixels of the image sensor is organized.
• the annular field-of-view between 50° and 100° maps to a linear distance of about 1.3 mm taken along one of the two orthogonal axes of the sensor grid.
• the lens may be configured and constructed such that a ray of the second angle in object space intersects the lens image plane at a distance, H, from the optical axis and a ray of the first angle in object space intersects the lens image plane at a distance, h, from the optical axis such that H/h > R, or preferably H/h > l . lxR, or more preferably H/h > 1.5xR.
• the lens may be constructed and arranged such that a ratio of a diameter (Di) at the image plane of an image circle of the full field-of-view versus the diameter (D1/2) of an image circle of the central half field-of-view is Di / D1/2 > 2. Also Di / D1/2 > 2.2, or preferably Di / D1/2 > 2.5, or more preferably Di / D1/2 > 3.
• seventy-five percent or more of pixel sensor elements of the image sensor may be disposed in the image region corresponding to the annular field-of-view between 50° and 100°.
• the angular mapping of the field of view in the region of interest onto the image plane may be substantially linear.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Lenses (AREA)
• Stereoscopic And Panoramic Photography (AREA)
• Instruments For Viewing The Inside Of Hollow Bodies (AREA)
• Endoscopes (AREA)

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• 2018
  • 2018-05-31 WO PCT/US2018/035328 patent/WO2018222827A1/en active Application Filing
  • 2018-05-31 AU AU2018275249A patent/AU2018275249B2/en active Active
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